What steps I took:

- upload the stl in prusa slicer
- split it into parts
- made the settings for multi extruders
- selected the right colour per extruder
- added the extrudeer to the stl files
- sliced all and started a print

So I saw some custom g.code mentioned above. Where to paste that? And will that help me printing with the colours? Any other advise? Thanks.
Can I group the same colours (see stl listing) together so less changes? I noticed I can move the stl to other location.. 

Some impressions of the print and settings I used now:

I've never heard of a limit, but honestly, I really don't know.

Posted by: @mike_gka

I have done some improvement to the Tool change G-code

; eliminate first tool change
{if previous_extruder != -1}
G0 Z{toolchange_z+10} F6000
M601 ; Pause
M400 ; wait until all moves are completed
; color notification
M117 Next color is { (extruder_colour == "#00FF00" ? "GREEN"
:(extruder_colour == "#FF0000" ? "RED"
:(extruder_colour == "#FFFF00" ? "YELLOW"
:(extruder_colour == "#0000FF" ? "BLUE"
:(extruder_colour == "#FFFFFF" ? "WHITE"
:(extruder_colour == "#000000" ? "BLACK"
:(extruder_colour == "#999999" ? "GRAY"
:(extruder_colour == "#D4AF37" ? "GOLD"
:(extruder_colour == "#C0C0C0" ? "SILVER"
:(extruder_colour == "#FF8000" ? "ORANGE"
:(extruder_colour == "#800080" ? "PURPLE"
:(extruder_colour == "#FF6600" ? "ORANGE"
:(extruder_colour == "#F0F0F0" ? "TRANSPARENT"
:(extruder_colour == "#800000" ? "BROWN"
:extruder_colour ))))))))))))))};
G4 S4 ; wait 4 seconds
M600
{endif}

This will eliminate the M600 when start printing.

And the printer will pause before every tool change and after resume (Click continue) the printer will show the next color on the display for 4 sec.

The issue, after loading the second colour, there's a slight shift, like 1mm down/left.

I tried the print 3 times, resliced, checked XY alignment, re-run calibrations, utterly cracked the poops...

Thought, a quick roll back might be worth a shot... bingo. Ugh... 🙄

Posted by: @patrick-b

hi , will test on the Core 1 😉 

Without autoloading it sounds like a PITA... I mean seriously, having to manually feed filament through a bowden every manual change, yucky.

This won't be an issue soon, I'll be grabbing a Core One L with INDX the second they're released. Can, not, wait.

Posted by: @mike_gka

I have done some improvement to the Tool change G-code

; eliminate first tool change
{if previous_extruder != -1}
G0 Z{toolchange_z+10} F6000
M601 ; Pause
M400 ; wait until all moves are completed
; color notification
M117 Next color is { (extruder_colour == "#00FF00" ? "GREEN"
:(extruder_colour == "#FF0000" ? "RED"
:(extruder_colour == "#FFFF00" ? "YELLOW"
:(extruder_colour == "#0000FF" ? "BLUE"
:(extruder_colour == "#FFFFFF" ? "WHITE"
:(extruder_colour == "#000000" ? "BLACK"
:(extruder_colour == "#999999" ? "GRAY"
:(extruder_colour == "#D4AF37" ? "GOLD"
:(extruder_colour == "#C0C0C0" ? "SILVER"
:(extruder_colour == "#FF8000" ? "ORANGE"
:(extruder_colour == "#800080" ? "PURPLE"
:(extruder_colour == "#FF6600" ? "ORANGE"
:(extruder_colour == "#F0F0F0" ? "TRANSPARENT"
:(extruder_colour == "#800000" ? "BROWN"
:extruder_colour ))))))))))))))};
G4 S4 ; wait 4 seconds
M600
{endif}

This will eliminate the M600 when start printing.

And the printer will pause before every tool change and after resume (Click continue) the printer will show the next color on the display for 4 sec.

Posted by: @sdhayes

This has been working pretty well for me but I'm still working out some of the little kinks.

Has anyone else seen the "A filament specified in the G code is either not loaded or wrong type" warning immediately after you tell the UI to print? I have PLA loaded in the printer and PLA specified in the slicer so it's not a "real" problem and I have found that simply clicking through the error message results in everything working just fine, so I'm wondering if it's maybe some sort of a recognition issue wrapped up in "faking" the multiple extruder arrangement.

As I said, clicking through it works just fine, I'm just wondering if it's something I have setup incorrectly.

I'm seeing the wrong filament error on a Core One, PETG is loaded and single extruder _PETG_ files have no issue.   The file name when doing manual multi-color contains .._PETG,PETG_.. yet the Wrong Filament error occurs and the second filament, which was PETG was under extruded when I chose to print anyway.